Archive for April, 2007

More on Incubation & Hatching

Monday, April 23rd, 2007

Mariah and eggs

Despite our unofficial motto at Imprints, specto subitus (expect the unexpected), it seems pretty safe to say that Mariah is done laying eggs for this year. Quite naturally we’ve received a lot of questions from our viewers asking when we can expect the eggs to hatch.

We can’t give an exact date (falcon egg hatching prediction is far from an exact science) but in general, the eggs should hatch about 33 days after incubation begins. Since Mariah laid her final egg on April 7 and began incubating a few days before that, we expect to see the eggs start to hatch around the second week of May. That means Mariah’s new family should all be out of their shells by Mothers Day.

The hatching process usually takes a couple of days, though it can go longer than three days (72 hours) in some cases. The eyas uses an egg tooth to break through the egg in a process called pipping. The hatching eyas uses its egg tooth like a chisel. First it pierces a membrane-like pouch at one end of the egg. The pouch holds air that the eyas uses to breathe while it finishes punching a hole through the shell. During pipping, the eyas turns and chisels, turns and chisels, until eventually it cuts off one end of the shell. Between bouts of pipping the eyas will rest, and it may vocalize while it’s pipping, especially if Mariah or Kaver are making their ee-chupping sounds.

The final round of pipping takes between 15 minutes and an hour. Because Mariah didn’t start incubating until the third egg had been laid, all four should hatch close together. In clutches of four, all the eggs usually hatch within two days. This is called synchronous hatching. Because of synchronous hatching all the eyases will be about the same size, and therefore about equally able to compete for Mariah and Kaver’s attention, which means they’re all likely to get fed enough to grow into healthy fledglings. We’ll talk more about the eyases’ early development in another article.

-Jess

Nest Box Update: Riding Out the Storm

Monday, April 16th, 2007

It’s not quite a scene from the Wild West, but there was a standoff of sorts in the nest box today.
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The weather’s nasty here, and Kaver’s been incubating the eggs for most of the morning and afternoon. As you can see, Mariah would like a turn.

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It’s no surprise that Kaver doesn’t want to give up his comfy seat. After all, it’s cold, wet and windy outside the nest box. Facing to the south, the nest box is protected from the winds in Rochester, which usually blow out of the west. It is getting a little bit wet inside the box, but that’s nothing compared to the messy slush of heavy snow and rain that’s been falling steadily all day in Rochester.

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Mariah’s not one to give up, though. For more than two hours she stood next to Kaver in the nest box, moving closer as time passed. Without doubt she’s been vocalizing, using her “wail” to try to get Kaver to move off the eggs. She even got so close it looked like she might sit right on top of him, but Kaver’s having none of it!

She usually gets her way, but not this time. In the end, Kaver stayed on the eggs, while Mariah left the nest box. Look closely at the roof in the upper left corner of the picture below and you’ll see where she went…
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-Jess

What Happened to Mariah’s Fifth Egg?

Tuesday, April 10th, 2007

Four Eggs Camera 1

It seems that the Rochester Falconcam has entered the Twilight Zone. Overnight, one of Mariah’s eggs vanished. A careful review of the images from the cameras didn’t yield any clues as to what might have happened. The only thing we know for sure is that yesterday there were five eggs, and today there are only four.

Four Eggs from Camera 2

The Rochester Falconcam team used Camera 1’s ability to pan and tilt to search the catwalk area just below the nest box. We were looking for shell fragments or any other indication that the egg might have been pushed out of the nest, but despite a detailed survey we found nothing. That leaves us to speculate as to the egg’s fate.

It is possible that the egg was damaged while it was being turned by one of the falcons. You’ll recall that falcons turn the eggs during incubation to ensure even heating of the egg. Earlier this year at a Peregrine nest in Ohio, one of the eggs was broken, so it’s possible that might have happened here too. If that’s the case, the most likely explanation for its absence is that she ate the egg, or what remained of it. The egg shell is a valuable source of calcium, and Peregrines often eat the shells after their young have hatched.

Some readers have wondered if Mariah might have discarded it because she realized it wasn’t viable. That’s unlikely. Peregrines, including Mariah, have been known to incubate eggs that turned out to be nonviable, even long after the other eggs in the clutch had hatched. Also, during reintroduction efforts, Peregrines’ eggs would often be taken for artificial incubation and “dummy” eggs put in their place. In those cases the falcons continued to brood the fake eggs as if they were real.

Even though we didn’t see any evidence of an egg when searching with our camera, it is still possible that it was ejected from the nest, either accidentally or on purpose. The camera has a couple of blind spots caused by objects that block the camera’s view of the catwalk, and the egg could be hiding behind one of those. Also, the weather may have played a role. If the egg was dropped onto the catwalk, the high winds at the top of the tower may have moved it out of camera range, or even blown it off the catwalk entirely.

The only way to learn more would be to make a visit to the nest box in person, and we won’t do that. Mariah is in the middle of brooding her eggs, and we don’t want to disturb her, certainly not for the sake of satisfying our curiosity. Unless there is some great calamity, no one will venture anywhere near the nest box until the eyases are removed to be banded in early June. Meanwhile, we’ll have to settle for speculation, and hope that the remaining eggs go on to hatch successfully.

-Jess

Fifth Egg on Easter Eve

Sunday, April 8th, 2007

Mariah’s five eggs

Look carefully at the group of eggs– there are two on the right, one behind the other, for a total of five!

Mariah continues to surprise us all this year! Sometime around 4:00 PM today, she laid the fifth egg of 2007, about 67 hours after her previous one. Since she laid the first egg on March 26, they’ve come at intervals of 50, 106, 60 and 76 hours respectively– an average laying period of 73 hours, or about 20 hours more than her normal 54 hour intervals, so she has us all completely flummoxed this time around.

Here’s another shot…
Mariah with five eggs

Four eggs are lined up in front, with the fifth egg hidden behind the second one (counting from the left). Mariah’s breast and the eggs in front make it hard to see, but if you take a close look you can just make it out.

Mariah’s been incubating the eggs for the past five days. Usually, Peregrines begin incubating when the next to last, or penultimate egg is laid. They do this to ensure that all of the eggs will develop together, and hatch at more or less the same time. With the fifth egg being laid five days after the third, it’s likely that it will hatch after the others. That may put the last eyas at a bit of a disadvantage since its other siblings will be bigger and stronger, but there’s probably no need to worry about that. Mariah has had other “late” eggs in past years and even the smallest of her offspring usually end up being just fine. One of the major reasons for that is because Kaver has proven to be a very good provider, even for the large broods that Mariah seems to like. He’ll certainly be busy with five hungry eyases to feed (to say nothing of feeding himself and Mariah), but he’s an old hand at it, and an excellent hunter, so we’re confident that he can repeat his performance of years past.
Five eggs in the nest box

I suppose the question of a sixth egg is appropriate. Mariah laid six last year, so it’s possible, and with her newfound unpredictability it would be foolish to think she’s done even now. We’ll see in a few days whether she’s going to surprise us again.

-Jess

Mariah’s Fourth Egg & a Brooding Shift Change

Thursday, April 5th, 2007

Mariah’s fourth egg of 2007
It looks like Mariah was laying this egg at the same time I posted my last article! How’s that for timing?

Mariah with her four eggs

You can click the small image at the left for another view. Careful observers of the cameras, especially Camera 2 (a night vision model), noticed that Mariah frequently changed her position within the scrape last night beginning around 8:15 PM local time. She settled down about five minutes later. That kind of restlessness is often associated with egg laying, so even though the first view of the egg wasn’t available until early this morning, we believe she actaully laid egg #4 around 8:20 PM on the 4th of April. As you can imagine, we’re all very excited here at the Rochester Falconcam!

Will there be a fifth egg? We’ll know in a few days…

Brooding shift change

In the meantime, here’s a great illustration of a brooding shift change (click the image to see the full-sized version). You can see Mariah “encouraging” Kaver to leave the eggs so that she can brood them. She does this by using a vocalization called a “wail”, which tells Kaver that she wants to take a turn on the eggs! You can read more about that in my article on incubation.

-Jess

Will There Be A Fourth Egg?

Wednesday, April 4th, 2007

Who can say? If Mariah were sticking to her “traditional” egg-laying schedule, we would have expected to see another one sometime in the afternoon. She is still looking fluffed up and even a little gravid, so it’s possible that she has another egg on the way. Since she’s clearly not keeping to her old pace, we’ll just have to wait and see.

I’ve consulted with some falcon experts and learned a couple of things. The first is that long egg-laying times are not quite as rare as the literature might seem to indicate. It happened at a couple of nests in Toronto, Canada, for example. In those cases, territorial disputes appear to have been the cause, but age, weather and external stresses can all cause egg laying to be delayed. The consensus seems to be that as female Peregrines get older the normal gap of 48 to 72 hours between eggs can stretch, sometimes quite a bit.

It is possible that Mariah laid an egg between the second and third ones that we see in the nest box. We don’t know of any alternate nest sites in the area though. Also, since laying the third egg (and even before) she has been exhibiting typical brooding behavior at the Kodak nest site. She’s also been here almost constantly, so if she did lay an egg elsewhere, it has almost certainly been abandoned.

Incubation shift change

In fact, Mariah and Kaver have both been spending a lot of time incubating the three eggs in the nest. The picture at the left, from earlier today, shows Kaver arriving at the nest to take over brooding from Mariah. In true falcon style though, Mariah has been doing most of the work, with Kaver taking over only for a couple of hours at a time. When he’s not taking his turn incubating the eggs, he stays near the nest. Usually he’s perched just outside the nest box.

Kaver incubating

This is a typical pose for Kaver when he’s brooding the eggs. Notice how he’s leaning a bit forward, with his tail up in the air? He sits that way so that he can get the brood patches on his breast in contact with the eggs. It’s the extra heat from the brood patches that causes the eggs to develop. If he just pressed his abdomen against the eggs he wouldn’t transfer enough heat for incubation to continue. So his posture is a clue to what’s going on in the nest.

So, keep your eyes on the Rochester Falconcam! Maybe Mariah’s on track to lay another egg, or maybe we’ll just have three this year. We’ll just have to keep watching and waiting for now.

-Jess

And Then There Were… Three!

Monday, April 2nd, 2007

Mariah with three eggs
Yes, that’s right my friend, THREE EGGS!

Wow, am I ever glad I hedged my bets in my previous article. Mariah has never gone this long between eggs, but that’s what’s great about watching these falcons– they always show you something new.

I’ll see what I can learn about such a long period between eggs, and share what I find with you when I do!

Specto Subitus! (Expect the Unexpected!)

-Jess

Incubation – Turning Eggs into Eyases

Sunday, April 1st, 2007

Remember in a recent article I said to expect the unexpected when watching falcons? Well, here’s another example.

When we talked about egg laying, I noted that Mariah had never laid fewer than four eggs since she and Kaver became a pair in 2002. It seems that there’s a first time for everything, though. Mariah has begun brooding, or incubating the two eggs she has laid. A Peregrine usually begins brooding when the penultimate egg is laid, but remember that Mariah usually lays her eggs about 54 hours apart. This year, her two eggs were laid 50 hours apart– a bit shorter than normal for her. It’s been more than 80 hours since she laid the second egg. Scientists have seen examples of eggs being laid more than 72 hours apart, but it’s very rare. We never say never here at the Rochester Falconcam (it kind of goes along with expecting the unexpected), but at this point it looks like Mariah’s done laying eggs for this year.

You’re probably out there yelling at your computer screen right now, “How do you know Mariah’s incubating the eggs, Jess?!?”

Mariah brooding
Well, that’s a good question, so thanks for asking! We know she’s begun brooding by watching her behavior. During incubation, one of the falcons will stay on the eggs almost full time. They only take short breaks, leaving the eggs uncovered for a few minutes. In an eight hour period today, the eggs were only left uncovered three times, for no more than three minutes each time. That means for more than 98% of the time the eggs have been covered. Since it’s not very cold outside today, it’s pretty clear that they’re actually incubating, not just protecting the eggs from chilly air.

As we discussed before, Mariah and Kaver take turns brooding the eggs. Mariah incubates about 2/3 of the time, often for four or more hours before Kaver relieves her. Males brood for shorter periods– typically 2 to 3 hours, and they brood less frequently. While one adult is brooding, the other may be out hunting. Brooding falcons still need to eat, after all. If they’re not hunting, the other falcon usually stays close to the nest. Sometimes while Mariah is brooding the eggs Kaver will bring her food that he has hunted. She’ll eat the food outside the nest while he takes a turn incubating, but then she’ll come back and take over– provided she can get him to move off the eggs. If he doesn’t move right away, she may stand in the nest box and wail at him. Wailing has different meanings for falcons, but in general it indicates dissatisfaction with the current situation. So if Mariah wails at Kaver while he’s incubating, it’s her way of telling him she’s not happy that he’s still sitting on the eggs. As with most other interactions between male and female Peregrines, Mariah usually gets her way, though sometimes it takes a while for him to get the message.

So, just how does incubation work?

Kaver incubating

Heat makes the eggs start developing. When the eggs reach about 98.6°F, or 37°C the egg begins changing into an eyas. Conveniently enough, a Peregrine’s natural body temperature is about 103°F, or 39.5°C, so to heat up the eggs all they need to do is to get some of that body heat onto the eggs. Now, a Peregrine’s feathers make very good insulation. That’s how they can stand to stay out in cold temperatures without freezing to death. But while those feathers keep the cold air away from the falcon’s skin, they also keep their body heat from getting out. So to incubate the eggs, the Peregrine carefully settles down, shifting from side to side to get the eggs beneath their feathers. Falcons have brood patches, areas on their breasts with a lot of blood vessels close to the surface of their skin. The blood vessels concentrate their body heat, making it easier to transfer the heat to the eggs. Both Mariah and Kaver have brood patches, though his are smaller than hers, which makes sense since he’s a smaller bird (if you’ve been following along with Imprints you’ll know why. If not, go back and read about sexual dimorphism in Falcon Identification 101).

Peregrines incubate their eggs for 33 to 35 days. In the early days of brooding it’s important to keep the eggs as close to their ideal incubating temperature as possible. Too hot or too cool and the eggs won’t develop properly. Later in the incubation process, proper temperature isn’t quite as important. In fact, after a couple of weeks the falcons will be able to leave the eggs uncovered for longer periods of time. Sometimes leaving the eggs uncovered frequently, or for long periods can mean that the eggs hatch a few days later than normal. That usually doesn’t happen with Mariah and Kaver, though. Their nest box is in a place where it’s not likely to be disturbed, so they most often incubate steadily until the eggs hatch.

Kaver turning the eggs

If you watch closely, you might see Mariah or Kaver get up, move around, then settle back down on the eggs. Sometimes they do this just to get into a different position, and maybe to give their legs a bit of a stretch, but often what they’re doing is turning the eggs. They turn the eggs to ensure that they get evenly heated. If the eggs aren’t heated evenly they may not develop, or they may develop abnormally. It’s also possible for the developing egg to stick to the inside of the eggshell. Turning the eggs keeps the egg membrane from sticking to the sides of the shell. Falcons turn the eggs using their bills and their feet. As you can imagine, they turn their eggs very carefully! If you’re watchful and lucky, you may get to see a picture of them turning the eggs. It may look like they’re stepping on the eggs or pecking at them, but now you know what’s really going on.

-Jess